The present invention relates generally to a matchplate molding machine of the type in which a vertically movable platen actuated by a hydraulic ram moves a drag flask upwardly into engagement with a cope flask and then pushes both flasks upwardly against a pressing head to compact the molding sand in the two flasks. A molding machine of this general type is disclosed in Hunter U.S. Pat. No. 3,342,253 and Hunter U.S. Pat. No. 3,506,058.
As disclosed in U.S. Pat. No. 3,342,253, rollers are located at the corners of the cope flask and ride on vertically extending rails which guide and support the cope flask during its vertical movement. It is conventional to have a pair of rollers at each of the eight corners of the box-like flask with the rollers of each pair engaging opposite sides of the rail to provide a very stable guiding structure. The rollers usually are supported on eccentric mounting shafts to enable the rollers of each pair to be adjusted for interchangeability with different machines.
In some machines, the vertically movable platen also is guided by rollers which ride along the rails. One roller is mounted at each of the four corners of the platen and engages one side of the rail to guide and stabilize the platen while still allowing the platen some freedom of lateral movement.
During operation of the machine, the flasks are vibrated to cause the sand to settle in the flasks. Because of the vibration and other factors, the rollers and rails wear, and grooves ultimately are formed in the rails.
To reduce wear and the need for frequent replacement of the rails, it recently has been proposed to retrofit the machines with sliding bearings or "slippers" which replace the conventionally-used rollers, the slippers being attached to the existing roller mounting shafts. While such slippers do in fact reduce wear of the rails, it is difficult to adjust the presently available slippers into proper sliding contact with the rails and to maintain such contact as the slippers wear. When the slippers themselves ultimately wear out, it is a very tedious and time-consuming task to remove the worn slippers and to install and properly adjust new slippers.